The level of the lake is controlled by Mercury Energy, the owner of the eight hydroelectric dams on the Waikato River downstream of Lake Taupō, using gates built in 1940–41. The gates are used to reduce flooding, conserve water and ensure a minimum flow of 50 m3/s (1,800 cu ft/s) in the Waikato River. The resource consent allows the level of the lake to be varied between 355.85 and 357.25 metres (1,167.5 and 1,172.1 ft) above sea level.[4]
Lake Taupō is in a caldera created mainly by a supervolcanic eruption which occurred approximately 25,600 years ago.[5] According to geological records, the volcano has erupted 29 times in the last 30,000 years.[6] It has ejected mostly rhyoliticlava, although Mount Tauhara formed from dacitic lava.
Taupō has been active for 300,000 years with a very large event known as the Oruanui eruption occurring approximately 25,600 years ago.[5] It was the world's largest known eruption over the past 70,000 years, ejecting 1170 cubic kilometres of material and causing several hundred square kilometres of surrounding land to collapse and form the caldera. The caldera later filled with water to form Lake Taupō, eventually overflowing to cause a huge outburst flood.[7]
Several later eruptions occurred over the millennia before the most recent major eruption, which was traditionally dated as about 181 CE from Greenland ice-core records. Tree ring data from two studies suggests a later date of 232 CE ± 5[8] and this is now accepted.[9] Known as the Hatepe eruption, it is believed to have ejected 100 cubic kilometres of material, of which 30 cubic kilometres was ejected in a few minutes. This was one of the most powerful eruptions in the last 5000 years (alongside the Minoan eruption in the 2nd millennium BCE, the Tianchi eruption of Baekdu around 1000 CE and the 1815 eruption of Tambora), with a Volcanic Explosivity Index rating of 7; and there appears to be a correlation, to within a few years, of a year in which the sky was red over Rome and China. The eruption devastated much of the North Island and further expanded the lake. The area was uninhabited by humans at the time of the eruption, as New Zealand was not settled by Māori until about 1280. Possible climatic effects of the eruption would have been concentrated on the Southern Hemisphere due to the southerly position of Lake Taupō.[10] Taupō's last known eruption occurred around 30 years later, with lava dome extrusion forming the Horomatangi Reefs, but that eruption was much smaller than the Hatepe eruption.
Underwater hydrothermal activity continues near the Horomatangi vent,[11] and nearby geothermal fields with associated hot springs are found north and south of the lake, for example at Rotokawa and Tūrangi. These springs are the site of occurrence of certain extremophile micro-organisms, that are capable of surviving in extremely hot environments.[12]
The volcano is considered active and is monitored by GNS Science.[13]
Native faunal species in the lake include northern kōura or crayfish (Paranephrops planifrons) and kōkopu or whitebait (Galaxias species). The lake is noted for stocks of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss), introduced from Europe and California respectively in the late nineteenth century. There has also been a subsequent introduction of smelt (Retropinnidae species) as a food for the trout.
A community of sponges and associated invertebrates live around the underwater geothermal vents.[11]
Tourism
NASA satellite photo of Lake TaupōWharf and small jetty where the Waikato River departs the lake, 1928Māori rock carvings at Mine Bay are over 10 metres high and accessible only by boat or kayak.
Tourism is a major component of Taupō's commercial sector. The busiest time for the industry is the high summer season around Christmas and New Year.
The lake area has a temperate climate. Daily maximum temperatures recorded for Taupō range from an average of 23.3 °C in January and February to 11.2 °C in July,[15] while the nighttime minimum temperatures range from 11.6 °C in February down to 2.2 °C in July.[16] Rain falls in all seasons but is greatest in winter and spring, from June to December.[17]
Taupō hosts the Lake Taupo Cycle Challenge, a cycling tour around the lake which can take anywhere between four and ten hours. Skydiving is a popular local sport and tourist attraction. Taupō also hosts the Kellogg's Ironman event.
Crossing the 40.2 km length of the lake is a challenge for open-water swimmers. In 2020, Michael Wells from Darwin, Australia, was the first to breaststroke across the lake.[18]
Māori rock carving
On the north-west side of Lake Taupō on the cliffs of Mine Bay, there are Māori rock carvings created in the late 1970s by Matahi Whakataka-Brightwell and John Randall. Carved in the likeness of Ngātoro-i-rangi, a navigator who guided the Tūwharetoa and Te Arawa tribes to the Taupō area over a thousand years ago according to Māori legend.[19] The 10-metre-high carving is intended to protect Lake Taupō from volcanic activities underneath. The cliff has become a popular tourist destination with hundreds of boats and yachts visiting the spot yearly.
Māori tribes
Lake Taupō is a taonga (treasure or something special to the person) of Ngāti Tūwharetoa from the Te Arawa waka. Ngāti Tūwharetoa owns the bed of the lake and its tributaries. They grant the public free access for recreational use.[20]
^Climate, History and the Modern World, Lamb, H. (1995), Routledge
^ abde Ronde, C. E. J.; Stoffers, P.; Garbe-Schönberg, D.; Christenson, B. W.; Jones, B.; Manconi, R.; Browne, P. R. L.; Hissmann, K.; Botz, R.; Davy, B. W.; Schmitt, M.; Battershill, C. N. (2002). "Discovery of active hydrothermal venting in Lake Taupo, New Zealand". Journal of Volcanology and Geothermal Research. 115 (3–4): 257–275. Bibcode:2002JVGR..115..257D. doi:10.1016/S0377-0273(01)00332-8.
^C.Michael Hogan. 2010. Extremophile. eds. E.Monosson and C.Cleveland. Encyclopedia of Earth. National Council for Science and the Environment, Washington DC
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